Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 9 de 9
Filtrar
Más filtros










Base de datos
Intervalo de año de publicación
1.
J Immunol ; 167(5): 2555-60, 2001 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-11509595

RESUMEN

Ag-specific immune tolerance in clinical organ transplantation is currently an unrealized but critical goal of transplant biology. The specificity and avidity of multimerized MHC-peptide complexes suggests their potential ability to modulate T cell sensitization and effector functions. In this study, we examined the ability of MHC-peptide dimers to modulate T cell function both in vitro and in vivo. Soluble MHC dimers induced modulation of surface TCR expression and inhibited T cell cytolytic activity at nanomolar concentrations in vitro. Furthermore, engagement of TCR by soluble dimers resulted in phosphorylation of the TCR zeta-chain and recruitment and phosphorylation of zeta-associated protein-70 to the signaling complex, the latter of which increased upon dimer cross-linking. Significantly, Ag-specific inhibition of an alloreactive TCR-transgenic T cell population in vivo resulted in consequent outgrowth of an allogeneic tumor. The prolonged Ag-specific suppression of expansion and/or effector function of cognate T cells in vivo suggests that soluble MHC dimers may be a means of inducing sustained Ag-specific T cell unresponsiveness in vivo.


Asunto(s)
Antígenos H-2/metabolismo , Linfocitos T Citotóxicos/inmunología , Animales , Citotoxicidad Inmunológica , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Dimerización , Antígenos H-2/química , Humanos , Tolerancia Inmunológica , Técnicas In Vitro , Ratones , Ratones Endogámicos BALB C , Ratones Noqueados , Ratones Transgénicos , Proteínas Nucleares , Proteínas Tirosina Quinasas/metabolismo , Receptores de Antígenos de Linfocitos T/genética , Receptores de Antígenos de Linfocitos T/metabolismo , Transducción de Señal , Linfocitos T Citotóxicos/metabolismo , Inmunología del Trasplante , Proteína Tirosina Quinasa ZAP-70
2.
Curr Protoc Immunol ; Chapter 17: Unit 17.2, 2001 May.
Artículo en Inglés | MEDLINE | ID: mdl-18432743

RESUMEN

The lack of high affinity reagents has made distinguishing T cells on the basis of antigen specificity difficult to accomplish. This unit provides protocols that utilize innovations in molecular design to permit construction of soluble multivalent MHC complexes (MHC-Ig dimers) with high avidity for cognate T cell receptors. MHC-Ig dimers display stable binding properties when they interact with antigen-specific T cells thus allowing their use in the staining of antigen-specific T cells by flow cytometry. Methods for constructing and detecting these MHC-Ig dimers are included along with protocols for applying their use for the quantitation of antigen-specific T cells.


Asunto(s)
Antígenos/inmunología , Linfocitos T CD8-positivos/inmunología , Antígenos de Histocompatibilidad Clase II/inmunología , Antígenos de Histocompatibilidad Clase I/inmunología , Inmunoglobulinas/inmunología , Animales , Antígenos de Superficie/inmunología , Clonación Molecular , ADN Complementario/genética , ADN Complementario/inmunología , Dimerización , Ensayo de Inmunoadsorción Enzimática/métodos , Citometría de Flujo/métodos , Vectores Genéticos/genética , Vectores Genéticos/inmunología , Antígenos de Histocompatibilidad Clase I/genética , Antígenos de Histocompatibilidad Clase II/genética , Humanos , Inmunoglobulinas/genética , Inmunoglobulinas/aislamiento & purificación , Reacción en Cadena de la Polimerasa/métodos , Receptores de Antígenos de Linfocitos T/inmunología , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/inmunología
3.
J Immunol ; 164(9): 4433-42, 2000 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-10779742

RESUMEN

CTLA-4 (CD152) engagement can down-regulate T cell activation and promote the induction of immune tolerance. However, the strategy of attenuating T cell activation by engaging CTLA-4 has been limited by sharing of its natural ligands with the costimulatory protein CD28. In the present study, a CTLA-4-specific single-chain Ab (scFv) was developed and expressed on the cell surface to promote selective engagement of this regulatory molecule. Transfectants expressing anti-CTLA-4 scFv at their surface bound soluble CTLA-4 but not soluble CD28. Coexpression of anti-CTLA-4 scFv with anti-CD3epsilon and anti-CD28 scFvs on artificial APCs reduced the proliferation and IL-2 production by resting and preactivated bulk T cells as well as CD4+ and CD8+ T cell subsets. Importantly, expression of anti-CTLA-4 scFv on the same cell surface as the TCR ligand was essential for the inhibitory effects of CTLA-4-specific ligation. CTLA-4-mediated inhibition of tyrosine phosphorylation of components of the proximal TCR signaling apparatus was similarly dependent on coexpression of TCR and CTLA-4 ligands on the same surface. These findings support a predominant role for CTLA-4 function in the modification of the proximal TCR signal. Using T cells from DO11.10 and 2C TCR transgenic mice, negative regulatory effects of selective CTLA-4 ligation were also demonstrated during the stimulation of Ag-specific CD4+ and CD8+ T cells by MHC/peptide complexes. Together these studies demonstrate that selective ligation of CTLA-4 using a membrane-bound scFv results in attenuated T cell responses only when coengaged with the TCR during T cell/APC interaction and define an approach to harnessing the immunomodulatory potential of CTLA-4-specific ligation.


Asunto(s)
Anticuerpos Bloqueadores/farmacología , Antígenos de Diferenciación/inmunología , Inmunoconjugados , Región Variable de Inmunoglobulina/inmunología , Activación de Linfocitos/inmunología , Receptores de Antígenos de Linfocitos B/inmunología , Abatacept , Secuencia de Aminoácidos , Animales , Anticuerpos Bloqueadores/biosíntesis , Anticuerpos Bloqueadores/genética , Anticuerpos Bloqueadores/metabolismo , Especificidad de Anticuerpos/genética , Antígenos CD , Antígenos de Diferenciación/metabolismo , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/inmunología , Antígeno CTLA-4 , Línea Celular , Citocinas/biosíntesis , Citocinas/metabolismo , Femenino , Humanos , Región Variable de Inmunoglobulina/biosíntesis , Región Variable de Inmunoglobulina/metabolismo , Interfase/genética , Interfase/inmunología , Ligandos , Activación de Linfocitos/genética , Complejo Mayor de Histocompatibilidad/genética , Complejo Mayor de Histocompatibilidad/inmunología , Ratones , Ratones Endogámicos BALB C , Ratones Transgénicos , Datos de Secuencia Molecular , Péptidos/genética , Péptidos/inmunología , Receptores de Antígenos de Linfocitos B/biosíntesis , Receptores de Antígenos de Linfocitos B/genética , Receptores de Antígenos de Linfocitos B/metabolismo , Receptores de Antígenos de Linfocitos T/inmunología , Receptores de Antígenos de Linfocitos T/metabolismo , Transducción de Señal/genética , Transducción de Señal/inmunología , Subgrupos de Linfocitos T/inmunología , Transfección , Células Tumorales Cultivadas
4.
Cell Immunol ; 192(2): 175-84, 1999 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-10087186

RESUMEN

T cell receptors (TCR) and major histocompatibility complex (MHC) molecules are integral membrane proteins that have central roles in cell-mediated immune recognition. Therefore, soluble analogs of these molecules would be useful for analyzing and possibly modulating antigen-specific immune responses. However, due to the intrinsic low-affinity and inherent solubility problems, it has been difficult to produce soluble high-affinity analogs of TCR and class II MHC molecules. This report describes a general approach which solves this intrinsic low-affinity by constructing soluble divalent analogs using IgG as a molecular scaffold. The divalent nature of the complexes increases the avidity of the chimeric molecules for cognate ligands. The generality of this approach was studied by making soluble divalent analogs of two different classes of proteins, a TCR (2C TCR2Ig) and a class II MHC (MCCI-Ek2Ig) molecule. Direct flow cytometry assays demonstrate that the divalent 2C TCR2Ig chimera retained the specificity of the native 2C TCR, while displaying increased avidity for cognate peptide/MHC ligands, resulting in a high-affinity probe capable of detecting interactions that heretofore have only been detected using surface plasmon resonance. TCR2IgG was also used in immunofluorescence studies to show ER localization of intracellular peptide-MHC complexes after peptide feeding. MCCI-Ek2Ig chimeras were able to both stain and activate an MCC-specific T cell hybridoma. Construction and expression of these two diverse heterodimers demonstrate the generality of this approach. Furthermore, the increased avidity of these soluble divalent proteins makes these chimeric molecules potentially useful in clinical settings for probing and modulating in vivo cellular responses.


Asunto(s)
Antígenos de Histocompatibilidad Clase II/metabolismo , Receptores de Antígenos de Linfocitos T/metabolismo , Proteínas Recombinantes de Fusión/metabolismo , Secuencia de Bases , Dimerización , Antígenos de Histocompatibilidad Clase II/química , Humanos , Hibridomas/inmunología , Inmunoglobulina G/metabolismo , Activación de Linfocitos , Datos de Secuencia Molecular , Receptores de Antígenos de Linfocitos T/química , Proteínas Recombinantes de Fusión/química
5.
J Exp Med ; 188(9): 1633-40, 1998 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-9802975

RESUMEN

The interaction of the T cell receptor (TCR) with its cognate peptide-major histocompatibility complex (MHC) on the surface of antigen presenting cells (APCs) is a primary event during T cell activation. Here we used a dimeric IEk-MCC molecule to study its capacity to activate antigen-specific T cells and to directly analyze the role of CD4 in physically stabilizing the TCR-MHC interaction. Dimeric IEk-MCC stably binds to specific T cells. In addition, immobilized dimeric IEk-MCC can induce TCR downregulation and activate antigen-specific T cells more efficiently than anti-CD3. The potency of the dimeric IEk-MCC is significantly enhanced in the presence of CD4. However, CD4 does not play any significant role in stabilizing peptide-MHC-TCR interactions as it fails to enhance binding of IEk-MCC to specific T cells or influence peptide-MHC-TCR dissociation rate or TCR downregulation. Moreover, these results indicate that dimerization of peptide-MHC class II using an IgG molecular scaffold significantly increases its binding avidity leading to an enhancement of its stimulatory capacity while maintaining the physiological properties of cognate peptide-MHC complex. These peptide-MHC-IgG chimeras may, therefore, provide a novel approach to modulate antigen-specific T cell responses both in vitro and in vivo.


Asunto(s)
Antígenos de Diferenciación de Linfocitos T/metabolismo , Antígenos de Histocompatibilidad Clase II/metabolismo , Activación de Linfocitos/inmunología , Linfocitos T/inmunología , Animales , Línea Celular , Dimerización , Regulación hacia Abajo , Inmunoglobulina G/metabolismo , Cinética , Ligandos , Complejo Mayor de Histocompatibilidad , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Péptidos/química , Péptidos/inmunología , Receptores de Antígenos de Linfocitos T/metabolismo , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/inmunología
6.
J Exp Med ; 186(8): 1333-45, 1997 Oct 20.
Artículo en Inglés | MEDLINE | ID: mdl-9334373

RESUMEN

Understanding the regulation of cell surface expression of specific peptide-major histocompatibility complex (MHC) complexes is hindered by the lack of direct quantitative analyses of specific peptide-MHC complexes. We have developed a direct quantitative biochemical approach by engineering soluble divalent T cell receptor analogues (TCR-Ig) that have high affinity for their cognate peptide-MHC ligands. The generality of this approach was demonstrated by specific staining of peptide-pulsed cells with two different TCR-Ig complexes: one specific for the murine alloantigen 2C, and one specific for a viral peptide from human T lymphocyte virus-1 presented by human histocompatibility leukocyte antigens-A2. Further, using 2C TCR- Ig, a more detailed analysis of the interaction with cognate peptide-MHC complexes revealed several interesting findings. Soluble divalent 2C TCR-Ig detected significant changes in the level of specific antigenic-peptide MHC cell surface expression in cells treated with gamma-interferon (gamma-IFN). Interestingly, the effects of gamma-IFN on expression of specific peptide-MHC complexes recognized by 2C TCR-Ig were distinct from its effects on total H-2 Ld expression; thus, lower doses of gamma-IFN were required to increase expression of cell surface class I MHC complexes than were required for upregulation of expression of specific peptide-MHC complexes. Analysis of the binding of 2C TCR-Ig for specific peptide-MHC ligands unexpectedly revealed that the affinity of the 2C TCR-Ig for the naturally occurring alloreactive, putatively, negatively selecting, complex, dEV-8-H-2 Kbm3, is very low, weaker than 71 microM. The affinity of the 2C TCR for the other naturally occurring, negatively selecting, alloreactive complex, p2Ca-H-2 Ld, is approximately 1000-fold higher. Thus, negatively selecting peptide-MHC complexes do not necessarily have intrinsically high affinity for cognate TCR. These results, uniquely revealed by this analysis, indicate the importance of using high affinity biologically relevant cognates, such as soluble divalent TCR, in furthering our understanding of immune responses.


Asunto(s)
Antígenos H-2/biosíntesis , Péptidos/inmunología , Péptidos/metabolismo , Receptores de Antígenos de Linfocitos T/biosíntesis , Animales , Unión Competitiva/inmunología , Biopolímeros/biosíntesis , Biopolímeros/inmunología , Biopolímeros/metabolismo , Cationes Bivalentes , Antígenos H-2/efectos de los fármacos , Antígenos H-2/metabolismo , Interferón gamma/farmacología , Ratones , Ratones Endogámicos BALB C , Ratones Transgénicos , Modelos Inmunológicos , Péptidos/efectos de los fármacos , Unión Proteica/genética , Unión Proteica/inmunología , Receptores de Antígenos de Linfocitos T/metabolismo , Proteínas Recombinantes de Fusión/metabolismo , Solubilidad , Células Tumorales Cultivadas
7.
Hum Immunol ; 51(2): 63-72, 1996 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-8960907

RESUMEN

The light chain of HLA class I protein (beta 2m) has been expressed in Aspergillus nidulans. The cDNA of beta 2m was modified using the polymerase chain reaction to include overlapping extensions for its subsequent fusion into an Aspergillus vector. This fusion resulted in beta 2m cDNA being flanked by the Aspergillus awamori glucoamylase promoter and the Aspergillus niger glucoamylase terminator. Expression of beta 2m was induced by the addition of starch to the culture medium. In preliminary mass culture trials, 177 micrograms/liter of f beta 2m were obtained in 60-liter fermentations. N-terminal sequencing of purified human beta 2m produced in fungi (f beta 2m) revealed that 28% of the purified protein was of proper sequence and 61% of the protein had an additional serine and lysine residue derived from the C-terminus of the fungal leader. Purified f beta 2m from culture supernatants appeared biochemically similar to beta 2m obtained from human urine (u beta 2m) as seen in immunoblot analysis. Functionally, f beta 2m effectively interacted as a subunit of class I MHC molecules. This was seen both in a sandwich ELISA for detecting properly folded HLA class I heavy chain and in assays showing cell-surface beta 2m exchange into the mouse class I MHC H-2Kd. In these experiments the biological activity of f beta 2m was indistinguishable from u beta 2m. The successful expression of biologically active beta 2m in A. nidulans suggests that fungal systems might be useful for the production of other active components of the HLA class I MHC complex.


Asunto(s)
Aspergillus nidulans/genética , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/farmacología , Microglobulina beta-2/biosíntesis , Microglobulina beta-2/farmacología , Transporte Biológico , Ensayo de Inmunoadsorción Enzimática , Vectores Genéticos , Humanos , Proteínas Recombinantes de Fusión/análisis , Microglobulina beta-2/análisis
8.
Appl Environ Microbiol ; 59(6): 1876-82, 1993 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-8328804

RESUMEN

A pathway of succinate fermentation to acetate and butanoate (butyrate) in Clostridium kluyveri has been supported by the results of 13C nuclear magnetic resonance studies of the metabolic end products of growth and the detection of dehydrogenase activities involved in the conversion of succinate to 4-hydroxybutanoate (succinic semialdehyde dehydrogenase and 4-hydroxybutanoate dehydrogenase). C. kluyveri fermented [1,4-13C]succinate primarily to [1-13C]acetate, [2-13C]acetate, and [1,4-13C]butanoate. Any pathway proposed for this metabolism must account for the reduction of a carboxyl group to a methyl group. Succinic semialdehyde dehydrogenase activity was demonstrated after separation of the crude extracts of cells grown on succinate and ethanol (succinate cells) by anaerobic nondenaturing polyacrylamide gel electrophoresis. 4-Hydroxybutanoate dehydrogenase activity in crude extracts of succinate cells was detected and characterized. Neither activity was found in cells grown on acetate and ethanol (acetate cells). Analysis of cell extracts from acetate cells and succinate cells by sodium dodecyl sulfate-polyacrylamide gel electrophoreses showed that several proteins were present in succinate cell extracts that were not present in acetate cell extracts. In addition to these changes in protein composition, less ethanol dehydrogenase and hydrogenase activity was present in the crude extracts from succinate cells than in the crude extracts from acetate cells. These data support the hypothesis that C. kluyveri uses succinate as an electron acceptor for the reducing equivalents generated from the ATP-producing oxidation of ethanol.


Asunto(s)
Clostridium/metabolismo , Hidroxibutiratos/metabolismo , Oxidorreductasas/metabolismo , Succinatos/metabolismo , Clostridium/enzimología , Etanol/metabolismo , Fermentación , Espectroscopía de Resonancia Magnética , Ácido Succínico
9.
Appl Environ Microbiol ; 59(3): 748-55, 1993 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-8481001

RESUMEN

Growth rates and culture conditions affect the molar yields of catabolic end products and cells of Succinivibrio dextrinosolvens growing on glucose. When growth in chemostats occurred, a trend toward decreased succinate and acetate formation, increased lactate formation, and a higher yield of cells correlated with an increase in the growth rate. End product and cellular yields on defined medium indicate a high maintenance requirement for S. dextrinosolvens and are consistent with energy conservation steps during the formation of acetate and succinate. Simultaneous carbon dioxide consumption and production were determined from batch studies with NaH14CO3, and the amounts were used to calculate a fermentation balance. These data also indicated that CO2 consumption lags behind CO2 production early in the growth phase, becoming equivalent to it toward stationary phase. Significantly more CO2 was fixed by S. dextrinosolvens when the organism was cultured in chemostats sparged with CO2. Formate is in part derived from free CO2 in the medium, as shown by 13C nuclear magnetic resonance studies, and may be sensitive to CO2 availability. Nuclear magnetic resonance data are consistent with the carboxylation of a C3 intermediate of the Embden-Meyerhof-Parnas pathway of glycolysis to a C4 compound to eventually form succinate.


Asunto(s)
Bacteroidaceae/metabolismo , Dióxido de Carbono/metabolismo , Glucosa/metabolismo , Acetatos/metabolismo , Bacteroidaceae/crecimiento & desarrollo , División Celular/fisiología , Fermentación/fisiología , Formiatos/metabolismo , Lactatos/biosíntesis , Ácido Láctico , Espectroscopía de Resonancia Magnética , Oxidación-Reducción , Succinatos/metabolismo , Ácido Succínico
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...